JPH0218310A - Preparation of zirconium-containing ceramic powder - Google Patents

Abstract

PURPOSE:To obtain ZrC-contg. ceramic powder of high purity simply and efficiently by mixing zircon powder with a C-contg. material in a specified proportion, heat-treating the mixture at high temp. in a nonoxidizing atmosphere under reduced pressure, and then pulverizing the heat-treated product. CONSTITUTION:Zircon powder is mixed with a C-contg. material (e.g. carbon black) in 2.3-4.5 proportion by molar ratio (C/SiO2) of C in the C-contg. material to SiO2 in the ZrO2 powder. The mixture is then heat-treated as it is or after it is molded at 1,200-2,000 deg.C in nonoxidizing atmosphere under reduced pressure. Thus, ZrC is generated by proceeding a reaction expressed by the formula, and SiO2 component in the ZrO2 is vaporized simultaneously as SiO vapor out of a reaction system. Thus, the reaction is proceeded in a short time and Zr carbide-contg. ceramic powder is prepd.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing zirconium-based ceramic powder, and in particular to a method for producing zirconium-based ceramic powder, and in particular, zirconium carbide (ZrC) powder and zirconium carbide-zirconium oxide solid solution (ZrC-Zr
0) Zirconium carbide ceramic powder such as powder, zirconium nitride (ZrN) FA powder and zirconium nitride-zirconium oxide solid solution (ZrN-Zr0)
) Powder, which is a zirconium nitride-based ceramic powder, is manufactured simply and efficiently from zircon powder.

Zirconium carbide and zirconium nitride not only have a high melting point of about 3400℃ and 3000℃, respectively, but also have a hardness of 2000kg/min and 1500kg/min, respectively.
Due to its excellent heat resistance and chemical stability, it is used as a material for various cutting tools and as special ceramics for high temperatures.

(Prior art) As a general method for producing zirconium carbide,
), ■ A method of heating and reacting zirconium tetrachloride (ZrC1n) with a hydrogen-hydrocarbon mixed gas, ■ Mixing zirconium oxide (ZrOz) with carbon, placing it in a graphite boat, and heating it in a Tammann furnace or high-frequency induction. 240 in the furnace
A method of heating to about 0°C; ■Zirconium-containing ores, such as zircon (ZrSiOa
) is mixed with carbon in excess of the theoretical amount and melted in an arc melting furnace at a temperature of 2000''C or higher in a reducing atmosphere.

However, in order to carry out the methods of ■ and ■, the raw materials Zr,
Since it is necessary to start from manufacturing ZrL or ZrC1a, the cost increases.

In addition, methods ① and ② require a large amount of energy because the processing temperature is high, at over 2000°C, and it also takes a lot of effort to crush the hardened product, so it is not energy-saving. There was a problem from that point of view.

Therefore, as an improvement measure for (1), Japanese Patent Application Laid-open No. 55-51713 discloses that a raw material containing zirconium silicate as a main component, such as zircon sand, is blended with carbon in excess of the theoretical amount and heated in an Acheson furnace. A method has been proposed in which zirconium carbide is obtained by producing zirconium carbide and SiC and separating them based on the difference in specific gravity.

This method has the advantage that not only the raw materials are cheap, but also mass production is possible, and since it can be manufactured at a lower temperature than the method using an arc melting furnace, it requires less labor for pulverization. However, on the other hand, it took time and effort to separate ZrC and SiC, and it was difficult to obtain a product with high purity.

Next, general methods for producing zirconium nitride include (1) a method of nitriding metal zirconium or zirconium hydride, (2) a method of adding zirconium tetrachloride as a reducing agent (A1.
(3) a method of nitriding zirconium oxide in the coexistence of carbon;
etc.

However, method 1) requires a large amount of energy to produce metal zirconium as a raw material, and is therefore not industrially practical. In particular, although nitriding of zirconium hydride is suitable for obtaining fine powder of zirconium nitride,
The reaction between zirconium hydride and nitrogen is an exothermic reaction and generates a large amount of hydrogen during the reaction, posing the risk of explosion. Furthermore, methods (1) and (2) require high-value Zr, ZrHt, or ZrC1m as raw materials, which adds to the disadvantage of increased costs.

In addition, in method (3), the raw material is relatively inexpensive Zr0z, so there is no cost problem, but the processing temperature is 2000
Because the temperature is high (over ℃), a large amount of energy is required, and the zirconium nitride powder and raw material zirconium oxide powder are sintered during the nitriding reaction, inhibiting the nitriding reaction and containing zirconium oxide. In addition to the disadvantage that the product remains, there are also other problems such as requiring a great deal of labor to crush the product.

Therefore, in Japanese Patent Application Laid-open No. 60-186407,
Regarding the method for producing zirconium nitride powder belonging to method (3), ZrN is combined with, for example, MgO, MgzN3 by heating zirconium oxide in a nitrogen stream in the presence of one or more alkaline earth metals (for example, Mg). A method has been proposed in which mixed powders are produced, treated with acid, washed with water, and then subjected to centrifugal separation to obtain ZrN powder.

This method uses Zr01, which has a relatively high skin price, as a raw material,
Although ZrN can be produced at low temperatures, additional steps such as acid treatment and the like are required to separate ZrN.

(Problem B to be Solved by the Invention) This invention advantageously solves the above-mentioned problems and provides a manufacturing method that enables mass production of zirconium carbide powder and zirconium nitride powder at low cost and efficiently without the need for a powder separation process. The first purpose is to propose the following.

A second object of the present invention is to propose a manufacturing method that can efficiently mass-produce zirconium carbide/zirconium oxide solid solution powder or zirconium nitride/zirconium oxide solid solution powder at low cost without requiring a powder separation process. The purpose of

(Means for Solving the Problem) As a result of extensive research into a method for producing high-purity zirconium carbide powder and zirconium nitride powder without the need for a powder separation process, the inventors found that using zircon as a raw material, It was found that by adding carbon to this in an appropriate proportion and then heat-treating it under reduced pressure, the SiO□ component in zircon can be efficiently removed as SiO vapor, thus achieving the above objective advantageously. .

In addition, during the above research to obtain zirconium carbide powder and zirconium nitride powder, if the blending ratio of zircon and carbon is changed, zirconium carbide-zirconium oxide solid solution powder and zirconium nitride-zirconium oxide solid solution powder also require a separation process. We have also discovered that it can be advantageously obtained without using the same method.

Here, zirconium carbide/zirconium oxide solid solution powder and zirconium nitride/zirconium oxide solid solution powder have a high melting point and high hardness similar to zirconium carbide and zirconium nitride, and also have excellent heat resistance and chemical stability. The sintered body produced using the above-mentioned powder is extremely useful for various cutting tools, special ceramics for high temperature use, etc.

During the above manufacturing process, zirconium silicide (Zr
It has also been found that it is more advantageous to perform the reduced pressure heat treatment at a lower temperature and higher pressure than the region where Si, Zr5Six, etc.) are generated.

This invention is based on the above knowledge.

That is, this invention combines zircon powder and carbon-containing material,
After mixing at a ratio that satisfies the molar ratio of carbon in the carbon-containing material (C/5iOz) to SiO2 in the zircon powder from 2.3 to 4.5, and making the resulting mixture as it is or into a molded body, 120 in a non-oxidizing atmosphere under reduced pressure
This is a method for producing zirconium carbide ceramic powder, which is characterized by subjecting the powder to heat treatment in a temperature range of 0 to 2000°C and then pulverizing it.

In addition, the zircon powder and the carbon-containing material are mixed at a molar ratio of carbon in the carbon-containing material to SiO2 in the zircon powder (C/5
iOz) mixed at a ratio that satisfies 2.3 to 3.5,
Production of zirconium nitride-based ceramic powder, characterized in that the obtained mixture is heated as it is or formed into a compact, heat-treated in a nitriding atmosphere under reduced pressure in a temperature range of 1200 to 2000°C, and then pulverized. It's a method.

Here, during the above manufacturing process, the heat treatment is performed at a temperature of 0. O1~0.6
A first stage heat treatment at a temperature of 1350-1550'C and a second stage heat treatment at a temperature of 1550-2000'C under atmospheric pressure.
It is particularly preferable that the treatment be performed by step heat treatment.

(Function) By performing heat treatment under reduced pressure according to the present invention, it becomes easy to volatilize the Sin and components in zircon as SiO vapor. For this reason, in the case of zirconium carbide ceramic powder, there is no need to reduce and carbonize the 5iOz component to SiC as in the method disclosed in JP-A-5B-51713 mentioned above, so the C/5iOz ratio should be 4.5 or less. This also eliminates the need for the process of separating ZrC and SiC.

Furthermore, zirconium nitride ceramic powder does not require any special additives as in the method disclosed in JP-A No. 60-186407, so no by-products are generated and therefore no separation step is required. It becomes.

Furthermore, the reaction time is shortened. The heat treatment time varies depending on the amount of treatment, but the reaction is sufficiently completed in about 2 hours.

The zircon powder used in this invention preferably has high purity and contains as few impurity components as possible other than ZrO and SiO□ components. For example, powder obtained by grinding ordinary zircon sand is advantageously suitable.

Regarding the particle size of the zircon powder, it is preferable that the particle size is smaller in order to promote the reaction with carbon quickly. Specifically, zircon powder with a purity of Zr0z + Sing of 98.5 wt% or more and a particle size of 44 μ- or less is preferable. is suitable.

Next, as carbon-containing materials to be mixed with the zircon powder, in order to maintain high purity of the resulting powder, the ash content remaining in the powder obtained after the vacuum heat treatment should be reduced (the lower the ash content is, the better; for example, petroleum coke, petroleum pitch, coal, etc.). Although pitch or carbon black are advantageously suitable, organic resins which generate carbon upon heating, such as phenolic resins and polyethylene, can also be used.

Now, the molar ratio of carbon in the carbon-containing material to SiO2 in the zircon powder is in the range of 2.3 to 4.5 for zirconium carbide ceramic powder and 2.3 to 3.5 for zirconium nitride ceramic powder. The reason for this is as follows.

The reaction between zircon and carbon follows the following equation.

% formula % ( ) Regarding zirconium carbide ceramic powder, in order to generate ZrC, it is necessary to proceed with the reaction of formula (4).

Further, in order to generate ZrO without generating ZrO, it is necessary to proceed with the reaction of formula (2). Therefore, ZrO
In order to produce zirconium carbide powder or zirconium carbide-zirconium oxide solid solution powder while suppressing the formation of , it is necessary to make the stoichiometric ratio C/5iOz 2.0 or more. However, in actual production, the molar ratio is 2.
．． If it is less than 3, 0 g of Zr will be mixed into the produced powder, so in this invention, the lower limit of the molar ratio is limited to 2.3. Similarly, in actual production, if C/5iOz exceeds 4.5, carbon becomes excessive and excess carbon remains in the produced powder, so the upper limit of C/5t (h was limited to 4.5).

By the way, in the Dokuyo Japanese Unexamined Patent Publication No. 55-51713, it was necessary to set the C/Stow to 6 to 8. Therefore Si
A subsequent separation step was required to avoid C contamination. It is advantageous for the blending ratio of carbon to be as close as possible to the theoretical value for ZrC formation, since excess carbon is less likely to remain.

In this respect, in this invention, when C/Stow is close to the theoretical value, Z
Since rC can be produced, powder with higher purity can be easily obtained.

The same applies to zirconium nitride ceramic powder, and in order to generate ZrN, it is necessary to proceed with the doffing (3) reaction. Further, in order to generate ZrO without generating ZrO, it is necessary to proceed with the reaction of formula (2). Therefore, in order to produce zirconium nitride powder or zirconium nitride/zirconium oxide solid solution powder while suppressing the generation of Zr0g, the lower limit of C/510g was set to 2.3. On the other hand, if C/510g exceeds 3.5, excessive carbon will be mixed into the resulting powder to advance the reaction (3), and ZrC will be generated by the reaction 4) and Therefore, in this invention, in order to obtain high purity powder, C/510g is mixed with 2.3
It was limited to a range of 3.5 to 3.5.

Note that the carbon in the carbon-containing material herein refers to fixed carbon that participates in the desiliconization reaction (desilification reaction) from which components that volatilize at temperatures below 1000° C. have been removed.

The mixture is then heat treated in a reduced pressure atmosphere either as it is or after being shaped, and it is important that this heat treatment be carried out under the following conditions.

First, the heat treatment temperature is in the temperature range of 1200 to 2000°C. This is because if the temperature is less than 1200°C, the desiliconization reaction will take a long time, resulting in poor productivity;
This is because if the temperature exceeds 0°C, not only will the energy cost for heat treatment increase, but also grain growth and sintering will proceed during the reaction.

The reduced-pressure atmosphere must be non-oxidizing to avoid burnout due to oxidation of carbon-containing materials, and in the case of zirconium carbide ceramic powder, the atmosphere must be non-oxidizing, excluding nitriding gases such as N2 and ammonia, and excluding non-nitriding gases such as Ar. An active gas atmosphere or a reducing gas such as methane gas or butane gas is used, whereas in the case of nitriding zirconium ceramic powder, a nitriding gas atmosphere is required to promote nitriding, such as N8 gas or ammonia decomposition gas, respectively. suitable.

Particularly suitable heat treatment conditions in this invention are as follows.

In this invention, the heat treatment is performed under reduced pressure, but preferably 0
．． The pressure should be in the range of 0.01 to 0.6 atm. That means the pressure is 0
．． This is because if the pressure is higher than 6 atm, it is difficult to effectively volatilize and remove SiO vapor, and 5iain SiC remains in the resulting powder, making it difficult to obtain a high-purity powder. Also, 0. O1
If the vacuum is higher than the atmospheric pressure, ZrO□ and SiO□ produced by the dissociation of zircon will be immediately reduced to the state of Zr+st, partly due to the presence of sufficient carbon as a reducing agent, and ZrSi, etc. This is because the removal of the SiO□ component in the SiO vapor state is inhibited. Therefore, it is desirable to carry out the desiliconization reaction at a lower temperature and higher pressure than the zirconium silicide production region without creating a high vacuum exceeding 0.01 atmosphere.

In the case of zirconium nitride ceramic powder, in order to carry out the nitriding reaction efficiently, it is desirable to make the nitrogen partial pressure as high as possible, preferably 0.01 atm or higher.

Furthermore, the heat treatment temperature was initially 1350 to 1550'C, and 5i (h component was volatilized outside the system,
It is preferable to raise the temperature to ~2000°C to promote high purity production of ZrC or ZrN.

(Example) Example 1 Zircon powder with an average particle size of 1.5 am with a total content of Zr0g and 5t(h) of 99.Owtχ, and carbon black 7 with an average particle size of 500 (fixed carbon 99-tχ ,
The molar ratio of fixed carbon in carbon black to Sin in zircon powder (C/S
After mixing thoroughly, a large number of cylindrical samples measuring 10 mm x 20 mH were prepared using a mold forming machine.

These molded bodies were subjected to vacuum desilicification treatment under various heat treatment conditions shown in Table 1, and the resulting powders were subjected to X-ray diffraction and chemical analysis. These results are also shown in Table 1.

As is clear from Table 1, Comparative Example 4 treated at 1 atm.
Not only silicon compounds such as SiC were present, but also unreacted ZrO and .Sin remained. Also, in Comparative Example 3, which was subjected to desiliconization treatment at a low temperature, unreacted ZrO2.5ift powder remained. Comparative Examples 1 and 2 where the carbon content is not appropriate also include Zr
O□ was generated (Comparative Example 1), and carbon remained (Comparative Example 2).

On the other hand, conforming examples 1 to 1 processed under the conditions according to the present invention
In each case, zirconium carbide powder or zirconium carbide-zirconium oxide solid solution powder could be produced with high purity.

Example 2 The total content of ZrOz and SiO□ was 99. Zircon powder with an average particle size of 1.5 μm and an average particle size of 5
00 carbon black 7 (fixed carbon 99w tχ,
Ash content 0. -tχ) is the molar ratio of fixed carbon in carbon black to SiO2 in zircon powder (C/5
iOz) in various proportions, thoroughly mixed, and then molded into 10 mmφ x 2011 III using a mold forming machine.
A number of cylindrical IH samples were prepared.

These compacts were subjected to vacuum desilinitriding treatment under various heat treatment conditions shown in Table 2, and the resulting powders were subjected to X-ray diffraction and chemical analysis. These results are also shown in Table 2.

Table 2 As is clear from Table 2, Comparative Example 9 treated at 1 atm.
Not only silicon compounds such as SiC were present, but also unreacted ZrO□ and SiO□ remained. Further, in Comparative Example 8, which was subjected to desiliconization treatment at a low temperature, unreacted Zr0z.5iOz powder remained. Comparative examples 5゜6 and 7 where the carbon content is not appropriate are also
ZrO□ was generated (Comparative Example 5), and carbon remained (Comparative Example 6.7).

On the other hand, conforming examples 8 to 8 treated under the conditions according to the present invention
All of No. 13 were able to produce zirconium nitride powder or zirconium nitride/zirconium oxide solid solution powder with high purity.

(Effects of the Invention) According to the present invention, high-purity zirconium carbide powder and zirconium nitride powder can be produced easily and efficiently (in large quantities) without the need for a separation process.

Further, according to the present invention, zirconium carbide-zirconium oxide solid solution powder and zirconium nitride-zirconium oxide solid solution powder can be easily and efficiently mass-produced without the need for a separation process, similar to zirconium carbide powder and zirconium nitride powder.

Furthermore, in the present invention, when producing the above solid solution powder, the ratio of zirconium carbide or zirconium nitride to zirconium monoxide can be easily changed by changing the blending ratio of zircon powder and carbon-containing material. .

Special permission Out wish Man river Saki made iron KK formula %formula%

Claims (3)

[Claims] 1. The zircon powder and the carbon-containing material are mixed at a molar ratio of carbon in the carbon-containing material to SiO_2 in the zircon powder (C/
SiO_2) is mixed at a ratio that satisfies 2.3 to 4.5, and the resulting mixture is made into a molded body or as it is, and then
1200-2000 in a non-oxidizing atmosphere under reduced pressure
1. A method for producing zirconium carbide-based ceramic powder, which comprises heat-treating in a temperature range of °C and then pulverizing. 2. The zircon powder and the carbon-containing material are mixed at a molar ratio of carbon in the carbon-containing material to SiO_2 in the zircon powder (C/
SiO_2) is mixed at a ratio that satisfies 2.3 to 3.5, and the resulting mixture is made into a molded body or as it is, and then
1200-2000℃ in a nitriding atmosphere under reduced pressure
1. A method for producing zirconium nitride ceramic powder, the method comprising heat-treating the powder at a temperature within the range of 100 to 100 ml, and then pulverizing the powder. 3. 13 where the heat treatment is at 0.01 to 0.6 atm.
First stage heat treatment at a temperature of 50-1550 °C and 1550 °C
The manufacturing method according to claim 1 or 2, comprising a second stage heat treatment at a temperature of -2000C.